Thiobacillus denitrificans, Micrococcus denitrificans, and some species of Serratia, Pseudomonas, and Achromobacter are implicated as denitrifiers. Pseudomonas aeruginosa can, under anaerobic conditions (as in swampy or water-logged soils), reduce the amount of fixed nitrogen (as fertilizer) by up to 50 percent.